The critical dimension varies with magnitude of damage/stress on the mandrel film (typically an organic film) during PE ALD processing in self-aligned multiple patterning. The CD directly impacts on device yield and managing the damage to the mandrel can help increase control of the CD into a predetermined range. In conventional ALD processing, process parameters, such as RF power and pressure, are optimized and fixed for damage in a certain range to obtain the acceptable CD performance. However, there is a risk that chamber to chamber matching will be poor because there is no variable knob in recipe structure.
Another requirement for spacer formation process in SAMP is a CD slimming capability to buffer wafer to wafer variation generated by earlier processing, such as lithography. The oxygen plasma in the same ALD chamber is typically used to slim the mandrel CD. The oxygen plasma slimming prior to deposition process, however, affects the overall productivity such as throughput and defect performance.
Accordingly, there is an ongoing need in the art for methods of controlling the critical dimension in self-aligned multiple patterning processes.